Most (LX/LH/OS/SN/LO/TP/SK/UA/AC...) star carriers charge YQ of around 900 USD for a J redemption from US to Europe. It's hard to imagine, that SK really pays this fee for the customer. Maybe some airlines like UA never ask FFPs for YQ payments, while other airlines like LX charge YQ to some programs like their own M&M or A3, but don't charge it to UA or SK (i.e. depending on agreement between airline and FFP). The only other explanation which makes commerical sense is that YQ is never charged for redemption tickets and some FFPs just keep it for themselves.